{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-34987",
        "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "state": "PUBLISHED",
        "assignerShortName": "GitHub_M",
        "dateReserved": "2026-03-31T19:38:31.617Z",
        "datePublished": "2026-04-09T18:48:33.552Z",
        "dateUpdated": "2026-04-10T14:12:55.374Z"
    },
    "containers": {
        "cna": {
            "title": "Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access",
            "problemTypes": [
                {
                    "descriptions": [
                        {
                            "cweId": "CWE-125",
                            "lang": "en",
                            "description": "CWE-125: Out-of-bounds Read",
                            "type": "CWE"
                        }
                    ]
                },
                {
                    "descriptions": [
                        {
                            "cweId": "CWE-787",
                            "lang": "en",
                            "description": "CWE-787: Out-of-bounds Write",
                            "type": "CWE"
                        }
                    ]
                }
            ],
            "metrics": [
                {
                    "cvssV4_0": {
                        "attackVector": "NETWORK",
                        "attackComplexity": "LOW",
                        "attackRequirements": "PRESENT",
                        "privilegesRequired": "LOW",
                        "userInteraction": "NONE",
                        "vulnConfidentialityImpact": "HIGH",
                        "vulnIntegrityImpact": "HIGH",
                        "vulnAvailabilityImpact": "HIGH",
                        "subConfidentialityImpact": "HIGH",
                        "subIntegrityImpact": "HIGH",
                        "subAvailabilityImpact": "HIGH",
                        "baseScore": 9,
                        "baseSeverity": "CRITICAL",
                        "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H",
                        "version": "4.0"
                    }
                }
            ],
            "references": [
                {
                    "name": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xx5w-cvp6-jv83",
                    "tags": [
                        "x_refsource_CONFIRM"
                    ],
                    "url": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xx5w-cvp6-jv83"
                }
            ],
            "affected": [
                {
                    "vendor": "bytecodealliance",
                    "product": "wasmtime",
                    "versions": [
                        {
                            "version": ">= 25.0.0, < 36.0.7",
                            "status": "affected"
                        },
                        {
                            "version": ">= 37.0.0, < 42.0.2",
                            "status": "affected"
                        },
                        {
                            "version": ">= 43.0.0, < 44.0.1",
                            "status": "affected"
                        }
                    ]
                }
            ],
            "providerMetadata": {
                "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
                "shortName": "GitHub_M",
                "dateUpdated": "2026-04-09T18:48:33.552Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1."
                }
            ],
            "source": {
                "advisory": "GHSA-xx5w-cvp6-jv83",
                "discovery": "UNKNOWN"
            }
        },
        "adp": [
            {
                "metrics": [
                    {
                        "other": {
                            "type": "ssvc",
                            "content": {
                                "timestamp": "2026-04-10T14:12:37.362283Z",
                                "id": "CVE-2026-34987",
                                "options": [
                                    {
                                        "Exploitation": "none"
                                    },
                                    {
                                        "Automatable": "no"
                                    },
                                    {
                                        "Technical Impact": "total"
                                    }
                                ],
                                "role": "CISA Coordinator",
                                "version": "2.0.3"
                            }
                        }
                    }
                ],
                "title": "CISA ADP Vulnrichment",
                "providerMetadata": {
                    "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
                    "shortName": "CISA-ADP",
                    "dateUpdated": "2026-04-10T14:12:55.374Z"
                }
            }
        ]
    }
}